Nststtjoatoe



BEST AVAILABLE com Sept. 14 1926.

F. H. MILLER INSULATOR Filed Jn. 8, 1921 INVENTOR Freder/c/r H. Miller.

ATTORNEY Patented Sept. 14, 19,25.

UNETED STATES BEST AVAlLABLE COP;

E ATENT OF FlCE.

FREDERICK H. MILLER, OF \VILKINSBURG, PENNSYLVANIA, ASSIGNOR Tb WESTING- ,HOUSE ELECTRIC &. IvIANUFACTURING COMPANY, A CORPORATION OF PENNSYL- INSULATOR.

Application filed January 8, 1921. Serial No. 435,809.

My invention relates to insulators and particularly to insulators of the pin type.

The object of my'invention is to provide a device of the above indicated character that shall be adapted for outdoor or other service Where conducting matter, such as rain, sleet or dust, islikely to accumulate'thereon and thatsliaILjmder such conditions, utilize the "insulating" 'alue of air to 'substantially a "maximum degree of efliciency.

"'Hertofora 'it has been usual to provide insulators of'the pintypehaving a single insulating member or a plurality of such 7 Tmmbjersmn one -o'r more of which petticoat 'portioiis 'are formed'to function as rain sheds aiid to' 'provide proper creepage distances.

Also; 'asset "forth in Patent No. 1,129,520, issued tb 'the' We"stingh0use' Electric & Manufacturing Company on an application filed by'Karl C. Randall, Sydney W. Farnsworth and Chas. Le G. Fortescue and in Patent No. 374,998, by Chas. Le G. Fortescue and George I L Gilcl1rest,' and assigned-to the ,Westin ghous'e Electric & Manufacturing Company, it has been usual to provide inseniors of the ''pin type havingequipoten- 'tial surfaces and surfaces conforming to the electrostatic 'fiow lines in a dielectric field.

Asset forth in the above mentionedpatents, when the sides of an insulator, extending between two zones or conductors of differentpotential, lie parallel to the electrostatic field, substantially the insulating value of air is obtained, and an obstruction in the field or an irregularity on the surface f the insulator ,will cause the concentration of dielectric stresses and thus, a breakdown of the field.

'However, for outdoor or other servicewhen conducting particles, such asrain,

sleetand dust, are likely to impinge against the insulating surfaces, it. has been found necessary to provide petticoats or othersimilarmeans to maintain the-surfaces dry and to give proper creepage distances under all conditions. Such etticoats, if disposed at random or in a haphazard 1nanner,'c0nstitute obstructions to the dielectric fieldwhich, as above mentioned, cause the field to break 'dowynat voltages belpw those which a re sustained by an insulator'having the petticoats properly formed and positioned.

Proper forming and positioning of the insulator petticoats is fully set forth in the above mentioned Patent No. 1,374,998 and cons sts principally in the forming of the etticoats to have surfaces 'atrightangles to the field. This construction prevents :the concentration of the field stresses at any particular points on the insulator andfpro'vides substantially the same dielectric strength as air, with theexcep'tion of the slight change in the specific inductive capacity of the space between the positions of difierent=potential in which the petticoats. are disposed.

One other exception to the mind petticoats having equi-potential surfaces do not disturb the dielectric field, as set forth in the above-mentioned Patent No. 1,374,998, is that there will be a tendency for-the dielecple that" edges of the petticoats. This tendency 'is overcome by extending the petticoats to positions in the field Where the latter'is relatively weak, so as to render the tendency of the stresses to concentrate a negligible factor for the particular field in which the-insula tor is located. I

In practicing my invention, I provide an insulator that may entirely, or for a greater portion of its length, utilize the dielectric strength of air in the manner set forth in the patent above mentioned. This is accomplished by eliminating all or a certain num ber of the petticoats to permit the main body surfaces to lie, unobstructed, in parallel relation to the f'eld. To protectthe body surfaces from the accumulation of conducting particles, such as rainor dust, and to compensate for the loss imereepage-surface distance caused by the elimination of the etticoats, I provide an insulating shell or cover-member of substantially bowl shape that conforms to the dielectric field and surrounds the insulator in spaced relation thereto.

In the accompanying drawings,"Figures 1 and 2 are similar views, partially in section and partially in elevation, of different forms Ofmy invention,

in an suitable manner, but is, preferably; provided with a vertically projecting tuhular portion 13 that may hegcernented in sposition in the lower end of the member 4. This 'onstruction'permits the insulator and the member 6 to be assembled an'd handled as a. Limit fAn. aperture, 'or apertures, 14 ma -be provitled at the bottom of the rnrn- *ber 6 to Eerie as drainiige means for su ch differ ofrionde'nsation iis tnay collect therein.

As eirblained inrthe'a'bove mentioned Patei'itNo. 'I,'3Y4;998,'tlie rpin'fi'iii' ay be ofnietul, or olf insulatingmtiteiial covered by metal, ohthejrfirer surfii'ce of the lower insulating member may he cotited with metal so as, in "co-operhtioh with the tie wire 10, to cause the dielectric "field to "assume a :precletermined su-ostim'tiall} bowl shape, similar to the contour 'pttthe insulator. ns shorrn. .Tlie upper instituting member '2 may he rprov'ided ivith the usual petticoat- 1-1 to function as a "rain'shed.

'The 'iiimbei' 6 is a h'otlo'tv body. also 'of howl sh'ape'to conform suhstzintially to the dielectric "iiel'd extending from a'position fia'cent to'theiperimeter'of th e ptticoat 11 to the pin 5. :This construct-ion protects the surfaces'of'the'ineinhus 2;3-hnd 4 from rain, snowfsleet and'dhst. These surfaces are iu the dilectiic field at a position. where it i comparatively strohtg'ahd, therefore. constitute the main insulating surfaces of the insulator. The outer surface of the member 6, being in the dielectric field at a position where the latter'is comparatively 'weak,'is less afl'etd by deposits of dust and other conducting matter. The edge 12 of the petti- 'coat 'l'lprojects beyond the'upperetlge of the member 6to-protect the latter, and is formed to cause rain to drip tree of thatmemher.

As shown in 2, in which the'struct'ure "is similar to that shown in Fig. '1, anfinsu- .lating filler 15 is disposedin thememher (-5 to maintain the-surfaces'ofl the members 2. 3 and. 4 absolutely *free of: moisture and other-deposits.

In this form, the po'rtiohlS extends to and over the..='uppe'r=.endjof;the pin 5 I While I'have shown and described 'p a rtieular forms of my invention, changesnayghe efipct it e e'i W h utdepar inat m the spirit andi's cope thereof. asset forth in the pfien d tdaim's I claim as my invention 1. An insulator comprising a main in:

BEST AVAILABLE COP sulating body structure shaped substantially throughout its length to conform to the electrostatic field thereof and an insulating, \routlier-protective envelope therefor shaped to conform to a,wealer portion of said field.

2. In an insulator, the combination with an insulating structure having a main body member of substantiz rlly bowl sl1ap e eon- .otisubstantia ly bowl shape confbifhi'n g to a diiie rent portion of said field, said body Lnember being disposed in said hollow mem- 3. In =ah insulator, the combination with an insulating structure hating pettieoat portion and a in'ainsbody p ortiqn thereunder coirformin rlto the "dielectric field j the 'sutator and having a bottom =openiiig' member having a tubular portir 1 dispofe in, and depending from, sa iaqp ieg a portion conforming to said field 1 pif'qfegtrijg from the hirer end of said tubulegqoprtiotji, in Sp nit isaid body rQitiom-tq position 1.1Ifder saidpettieoat f'port-ion', adja tent to the perimeteptfhereei QM-:3

4. An insulator ofthe pin -typecompr e s a main y trust r henna-were? of substantially bowl shape the sides of rwhi diverge laterallyjrom the lobi?itiliiiiizil"axis Y and imiwemauy away. i m. the, base, o

theipi and a ol ew-il e t membe similar shape constituting substantially 'completerj e'iiclosing envelope 'for the sides a'fid oneend thereofi A l 5. An insulator for disposition bet: gen two-zones 'otditterenhpotential a; di glee tr'ic {field of 'any predetermined cornl'iirising a member of.- insu-l'atingjlil aterial having a portion shaped substantially throughout lengthto eontorm to the normal eleetrostatie field between saidjzones, and 'a similar member enclosing the same in soacedrelation thereto. H J A 6. An insulatpr for disposition between o or (new o e ial immat trie field of any predetermined form-gem prising amain body n emberof insulatinp "iio material having its outer surface sliaped substantially throughout its length to conform to the normal electrostatio fieldbetween said zones, :1 similar member eiielosin; the, sa ne in spaced relation defame,

h r it fieldo firm i-fate in a'if'eakr v -3 1: 3/ .1 L L t een sard zones and a port on shaped to cript d-him sire-- 'iao- 1,599,580 BEST LABLE COP:

- the main body structure in spaced relation thereto.

8. An insulator structure comprising a a main body portion constructed substantially throughout its length to conform to the dielectric field in which it is disposed and a member formed in accordance with a weaker portion of said field and surrounding said body port-ion.

In testimony whereof! I have hereunto subscribed my name this 30th day of Deceml5 ber 1920.

FREDERICK H. MILLER. 

